Flexible heat cable device

ABSTRACT

A cooling apparatus for cooling an electronic device to be cooled includes a heat collector device which is in thermal contact with the electronic device, a heat sink for absorbing heat which is emitted from the heat collector device and comprising a condenser unit and a thermal interface unit, wherein the condenser unit is cooled down via the thermal interface unit, and a heat transfer device made from a flexible material for transferring heat which is emitted from the heat collector device to the heat sink. The thermal interface unit is designed as a thermal plug for connecting the condenser unit of the heat sink thermally and removably to an external cooling means.

RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to European PatentApplication No. 06026855.4 filed in the European Patent Office on 23Dec. 2006, the entire contents of which are hereby incorporated byreference in their entireties.

TECHNICAL FIELD

The present disclosure relates to a cooling apparatus, especially forcooling an electronic device, and to a cooling method. Exemplaryembodiments include a flexible heat transfer device for coolingelectronic devices to be cooled using a heat sink which is locatedremotely from the electronic device to be cooled. In particular, thepresent disclosure relates to thermosyphon, in which two-phase heattransfer means are enclosed.

A major aspect of a flexible heat transfer device which can be made froma flexible material is to define a flexible thermal path betweenelectronic devices to be cooled and heat sinks. Such a mechanicalflexibility allows easy routing and attaching of the heat cable indifferent geometric configurations of an electronic circuit.

BACKGROUND INFORMATION

A flexible thermosyphon device is described in Electronics CoolingMagazine, February 2006 (http://www.electronics-cooling.com/html/2006led a3.html). The disclosed thermosyphon device consists of a boiler, acap, a tube and a 100 mm×100 mm condenser. The device allows a flexiblearrangement between a heat source (i.e. an electronic component to becooled) and a heat sink.

Another conventional flexible heat pipe is disclosed in“http://sbir.gsfc.nasa.gov/sbir/successes/ss/100text.html”. Thedisclosed flexible heat pipe consists of a modular clamp-on plate, aflexible heat pipe code plate and a thermal bus receptacle. The heatpipe provides a mechanical support and a transfer of waste heat from aspace station equipment to a thermal bus.

In the U.S. Pat. No. 5,642,776, a heat pipe in the form of a simple foilenvelope and a method of construction such a heat pipe are disclosed.Two metal foil sheets coated with a plastic material are sealed togetheron all four edges to enclose a semi-rigid sheet of plastic film, and theenvelope is evacuated and loaded with a suitable quantity of liquid toact as a heat pipe.

The device disclosed in U.S. Pat. No. 5,642,776 operates as a heatspreader for an integrated circuit chip placed in contact with theenvelope surface. The heat is transferred across the plastic coatingwith only a small temperature differential. A foam plastic wick withchannels efficiently transports condensed liquid back to the heat inputlocation for evaporation. Some liquid, in particular that transported tothe surface of the foam wick, is vaporized by the applied heat, and thatliquid is continuously replaced by the capillary action of the wick andthe channels. A disadvantage of the envelope heat pipe device disclosedin U.S. Pat. No. 5,642,776 is that the materials in the heat pipe arebad conductors of heat such that the heat conductivity is decreased.

In U.S. Pat. No. 4,565,243, a heat pipe is disclosed, which isconstructed to be bent to conform to a particular mechanicalconfiguration after it is constructed. A wick in the evaporator regionis constructed from sintered metal powder, while the wick in anotherregion of the heat pipe is constructed with a screen wick to permitbending the pipe without destruction of the wick.

The disclosed heat pipe comprises a completely enclosed casing ofsufficiently thin and ductile material to permit bending of the casingat least once without rupture of the casing. Furthermore, the heat pipecomprises first and second wick structures, wherein the second wickstructure consists of at least two separate screen layers. The outerscreen layer is sintered to the inside surface of the casing and theother layer is located in intimate contact with the outer layer. Anappropriate heat transfer fluid is provided in the heat pipe.

The U.S. Pat. No. 4,345,642 discloses an articulated heat pipe wherein amultiple section heat pipe has flexible junctions between the sections.The individual sections are independent individual heat pipes configuredto interlock with each other at rotatable joints filled with a liquidhaving a high heat conductivity. A clearance between the sections ismaintained small enough to establish capillary forces that maintain theconductive liquid in place and also to minimize the temperaturedifferential across the rotating joint.

The thermal operation of the system depends only upon conventionaloperation of the heat pipes, such that a condensing section of heat pipeis located on one side of the rotating junction, while the evaporatingregion of the other heat pipe is in contact with the other side of thejunction. A thin layer of conducting fluid spread over the relativelylarge surface area of the cylindrical geometry of the fluid gapmaintains a minimal temperature difference between the co-acting regionsof the two heat pipes.

The U.S. Pat. No. 4,961,463 discloses a thermosyphon for removing heatfrom a permafrost foundation. The device can be installed in a frozenfoundation with an evaporator section disposed either horizontally orwith a negative slope, thereby allowing the evaporator section of thethermosyphon to be buried in a more shallow location of the foundation.The device comprises a condensate collecting ring device whereincondensate flows downwardly along a inner wall surface of a condensersection and collects in an inner ring. The ring slopes downwardly fromthe horizontal such that a condensate is collected a low point thereof.A condensate return tube communicates with the collector ring at the lowpoint thereof and ducts the condensate into the evaporator section to adesired location within the evaporator section. The condenser returntube has a length which acts to deposit the condensate at the desiredlocation within the evaporator section.

A major disadvantage of conventional cooling systems is that electroniccomponents to be cooled cannot be replaced in an easy and efficientmanner.

SUMMARY

A cooling means with a high flexibility is disclosed.

A cooling apparatus is disclosed for cooling an electronic device to becooled, comprising: a) a heat collector device which is adapted to be inthermal contact with the electronic device; b) a heat sink for absorbingheat which is emitted from the heat collector device and comprising acondenser unit and a thermal interface unit, wherein the condenser unitis cooled down via the thermal interface unit; c) a heat transfer devicemade from a flexible material for transferring heat which is emittedfrom the heat collector device to the heat sink, wherein d) the thermalinterface unit is designed as a thermal plug for connecting thecondenser unit of the heat sink thermally and removably to an externalcooling means.

A method for cooling an electronic device to be cooled is disclosed,comprising the following steps: a) collecting heat from the electronicdevice to be cooled by a heat collector device which is in thermalcontact with the electronic device to be cooled; b) transferring heatwhich is emitted from the heat collector device to a heat sink by meansof a heat transfer device made from a flexible material c) absorbingheat which is emitted from the heat collector device by means of theheat sink comprising a condenser unit and a thermal interface unit, thethermal interface unit being a thermal plug for connecting the condenserunit of the heat sink thermally and removably to an external coolingmeans; and d) cooling down the condenser unit via the thermal interfaceunit.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present disclosure are depicted in thedrawings and are explained in more detail in the following description.In the drawings, like or similar elements bear like reference numerals.

FIG. 1 is a principle block diagram for illustrating the function of athermosyphon;

FIG. 2 illustrates a flexible heat cable device arranged between powerelectronics module and a cooling system according to an exemplaryembodiment of the present disclosure;

FIG. 3 illustrates a flexible heat cable device depicted in FIG. 2 andshown disassembled;

FIG. 4( a) illustrates a heat collector device which is attached to theheat transfer device according to an exemplary embodiment of the presentdisclosure;

FIG. 4( b) shows a detail of the heat collector device depicted in FIG.4( a);

FIG. 5 illustrates a condenser unit as a part of a heat sink in across-sectional view;

FIG. 6 illustrates details of liquid channels of the condenser unitshown in FIG. 5;

FIG. 7 is a cross-sectional view of a condenser unit of anotherexemplary embodiment of the present disclosure showing a liquid returnhose;

FIG. 8 shows a condensate collector which is included in the condenserunit shown in FIG. 7;

FIG. 9 is another detailed view of the condenser unit shown in FIG. 7;

FIG. 10 illustrates a liquid-cooled cylindrical condenser unit withdirect contact to cooling water;

FIG. 11 is a cross-sectional view of the heat sink mounted to theflexible heat cable device shown in FIG. 10;

FIG. 12 is a condenser unit according to yet another exemplaryembodiment of the present disclosure using a unit for pumping condensedliquid; and

FIG. 13 shows details of a water-driven pump unit arranged in the heatsink of the flexible heat cable device shown in FIG. 11.

DETAILED DESCRIPTION

According to an aspect of the disclosure, an open-ended heat transfermechanism is provided, which is only completed with an external coolinginterface similar to an electrical instrument which is delivered to acustomer with a power plug.

Various condenser-side interfaces may be provided. Thus the essentialconcept of the present disclosure is to provide a flexible heat cabledevice which is capable of acting as a thermal equivalent of electricalcables and which has an increased flexibility in an overall mechanicaldesign of power electronics systems.

According to an aspect of the present disclosure a cooling apparatus forcooling an electronic device to be cooled comprises a heat collectordevice which is in thermal contact with the electronic device, a heatsink for absorbing heat which is emitted from the heat collector deviceand comprising a condenser unit and a thermal interface unit, whereinthe condenser unit is cooled down via the thermal interface unit, and aheat transfer device made from a flexible material for transferring heatwhich is emitted from the heat collector device to the heat sink.

It is an advantage of the present disclosure that the thermal interfaceunit is designed as a thermal plug for connecting the condenser unit ofthe heat sink thermally and removably to an external cooling means.

According to a further aspect, a method for cooling an electronic deviceto be cooled comprises the following steps: (i) collecting heat from theelectronic device to be cooled by a heat collector device which is inthermal contact with the electronic device to be cooled; (ii)transferring heat which is emitted from the heat collector device to theheat sink by means of a heat transfer device made from a flexiblematerial; and (iii) absorbing heat which is emitted from the heatcollector device by means of a heat sink comprising a condenser unit anda thermal interface unit, wherein the condenser unit is cooled down viathe thermal interface unit. The thermal interface unit is designed as athermal plug for connecting the condenser unit of the heat sinkthermally and removably to an external cooling means and an externalcooling bus, respectively.

In line with one exemplary development of the present disclosure, theheat transfer device includes an electrical connection unit tosimultaneously transfer thermal and electrical energy between theelectronic device and the heat sink.

In line with a further exemplary development of the present disclosure,the electronic device is soldered to the heat collector device.

In line with yet another exemplary development of the presentdisclosure, the heat transfer device can be made of a thermoplasticpolymer.

In line with yet another exemplary development of the presentdisclosure, the heat transfer device can be made of at least one ofpolyethylene, polyethylene-terephthalate and polystyrene.

In line with yet another exemplary development of the presentdisclosure, the heat transfer device includes a metal layer deposited onthe outer surface of the heat transfer device.

In line with yet another exemplary development of the presentdisclosure, the heat transfer device is made of super-elastic alloys.

In line with yet another exemplary development of the presentdisclosure, the condenser unit comprises a pump unit for pumping backliquid, which has been collected in a condensate collector.

In line with yet another exemplary development of the presentdisclosure, the pump unit of the condenser unit is driven by the flow ofcooling water.

In line with yet another exemplary development of the presentdisclosure, the heat sink and the heat transfer device form athermosyphon device.

In line with yet another exemplary development of the presentdisclosure, the heat sink is cooled by a secondary circulation ofcooling water.

In line with yet another exemplary development of the presentdisclosure, the heat transfer device transfers heat from the heatcollector device to the heat sink by transporting a liquid coolant fromthe heat collector device to the heat sink and by returning evaporatedcoolant from the heat sink to the heat collector device.

In line with yet another exemplary development of the presentdisclosure, the condenser unit of the heat sink is directly cooled bythe circulating cooling water.

The present disclosure in particular is related to cooling of powerelectronic systems and low voltage devices. In power electronic systems,a significant amount of heat can be generated within a small volume suchthat the generated heat must be dissipated to the environment.

Instead of attaching the heat generating components directly to a heatsink, an intermediate mechanism of heat transfer in the form of aheat-carrying cable is used to separate the source and the sink ofthermal energy.

This kind of separation assists in the mechanical design of powerelectronic systems. In addition to that, the heat cable can also be usedto adapt standard products to special customer requirements, forexample, by interfacing a drive to the customer's own cooling system.

The present disclosure now will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the disclosure are shown.

Two-phase heat transfer systems utilize liquid-vapour phase exchangeprocesses for increased heat transfer between a heat source and aworking fluid, and between a heat sink and the working fluid,respectively. Two-phase heat transfer components are heat pipes andthermosyphons.

FIG. 1 shows a block diagram for explaining the operation of athermosyphon. An electronic device 101 to be cooled is attached to anevaporator unit 102. It is noted that different electronic devices 101may be connected to a series of evaporator units 102 which in turn areconnected to a single condenser unit 103. An arrow 301 in FIG. 1 showsthe heat transfer direction. The heat is transferred from the evaporatorunit 102 to the condenser unit 103 which is cooled by cooling water 106.

A thermal contact between the evaporator unit 102 and the condenser unit103 is established by a liquid-vapour circulation in which a liquid(cooling liquid) 104 is evaporated in the evaporator unit 102 by heatwhich is transferred to the evaporator unit 102 from the electronicdevice 101 to be cooled. The evaporated liquid (as vapour 105) istransferred back to the condenser unit 103 where it is condensed againinto liquid 104.

The principle of exchanging liquid and vapour, respectively, between aheat source 101, 102 and a heat sink 103 is used for a flexibleconnection of electronic devices 101 to be cooled in a circuit, inparticular in a power circuit, and to flexibly transfer heat to a remoteheat sink 103, 200. Usually, the electronic device 101 to be cooled isattached to a heat collector device 100 which acts as an interfacebetween the electronic device 101 to be cooled and the evaporator unit102.

FIG. 2 illustrates the heat cable arranged between a power electronicsmodule and a cooling system. Reference numeral 101 denotes the powerelectronics module, i.e. the electronic device to be cooled. It is notedthat more than one electronic device can be connected to a respectiveheat sink 200 using a heat transfer device 300.

The flexible heat cable device shown in FIG. 2 is according to a firstexemplary embodiment of the present disclosure. The flexible heat cabledevice consists of a heat collector device 100 which is brought intothermo-contact with the electronic device 101 to be cooled. The heattransfer device 300 is used to transfer heat in the electronic device101 to a heat sink 200 which essentially consists of a condenser unit103. A connector unit 107 is provided to fix the heat transfer device300 detachable at the condenser unit 103.

The flexible heat cable device is configured in a similar fashion toelectrical cables, but it is used to transfer thermal energy instead ofelectrical energy. In an exemplary deployment of the present disclosure,the flexible heat cable device comprises an electrical cable as anelectric connection to simultaneously transfer thermal and electricalenergy between the electronic device 101 and the heat sink 200. It is anadvantage to construct the heat transfer device 300 from materials thehigh mechanical flexibility, thus permitting to route and attach theheat cable device in different geometrical configurations. Theconstruction of the heat transfer device as a heat cable is discussedbelow.

An important application for the heat cable device is, besides coolingof electronic devices, cooling of high power electronic systems such asmotor drives. To this end, the heat cable device can be used within thecasing of a drive system to transfer heat between an IGBT module (IGBT,Insulated Gate Bipolar Transistor) and a water or air heat exchanger.The mechanical design of the whole system is facilitated due to thecapability of the flexible heat cable device which allows routing of thecable within the casing and permits a separation of heat sources andheat exchangers. When a heat carrying cable is flexible, a suitablydesigned heat cable can be mass-manufactured and used in differentdevices.

The heat cable can also be routed out of the system casing and can beattached to an auxiliary heat exchanger, which can be shared by multiplesystems. It is an advantage of the present disclosure, that differentinterfaces are provided to permit an adaptability of the heat cabledevice.

FIG. 3 shows the flexible heat cable device of FIG. 2 in an explosiveview. A sealing unit designed as an O-Ring is provided to seal the heatsink 200 to the heat transfer device 300.

FIGS. 4( a) and 4(b) illustrate the heat collector device 100 of theflexible heat cable device shown in FIGS. 2 and 3. The heat collectordevice 100 can be designated as a “boiling” section. The boiling sectionis a chamber that is partly filled with the working fluid 104. Multiplecomponents can be attached at the bottom and/or the side walls of thischamber. The chamber can be made of a material such as copper, brass,aluminum, etc., which has a high thermal conductivity. The selection ofthe material of the boiling section depends on the compatibility withthe working fluid and on strength requirements.

As most electronic components, i.e. electronic devices 101, have aplanar geometry with one side used for electrical interfacing and theother for thermal interfacing, the boiling section comprises one flatsurface. In this case, a thermal base-plate of the component is used tospread the heat to a larger area and to add to a thermal capacitance foran improved temperature stability when a fluctuating heat dissipation isencountered.

According to another exemplary embodiment of the present disclosure, theboiling section can also be integrated into this base-plate module. Thismeans that the substrate of the power module can be directly soldered tothis boiling section. Thus, the whole power module can be delivered by asemi-conductor manufacturer in one piece together with the boilingsection, wherein an interface or opening to the heat transfer device 300is provided.

In yet another exemplary embodiment of the present disclosure, a bottomface of the boiling section can be opened such that a cavity which isable to receive liquid is only formed when the boiling section isattached to the module base-plate. The liquid is in direct contact withthe module base-plate. O-Ring or gas-cap-type seals can be used at theperiphery of the base-plate in order to provide a vacuum-tight sealing.

The heat transfer device 300 consists of a flexible conduit which isattached to the chamber to provide a gas-type conduit between the boilerand the condenser. There are different alternatives for the conduitconstruction. One possibility is to use a corrugated metal hose as shownin FIGS. 2 and 3.

These kind of corrugated metal hoses are found in vacuum equipment.These hoses can withstand vacuum and high pressure at elevatedtemperatures. Most importantly, the solid metal hose is inherentlygas-tight and is suitable for long term containment of a vacuum. This isa critical issue for power electronics equipment which have long termlife-time expectancies.

In yet another exemplary embodiment of the present disclosure, theconduit which forms the heat transfer device 300 is made from athermoplastic polymer. More preferably, the conduit is made frommaterials such as polyethylene, polyethylene-tereftalat,polyvinylchloride and polystyrene.

In yet another exemplary embodiment of the present disclosure, theconduit which forms the heat transfer device 300, is deposited by one ormore layers of metal. Preferably, aluminium is chosen as a suitablecoating material because of costs and ease of fabrication. Furthermore,a multi-layer coating can be applied.

In addition to that the heat transfer device can be constructed fromsuper-elastic alloys which have an enhanced intrinsic flexibility.Advantageously, the super-elastic alloys are metals and thus offer aleak-proof seal. Complete strain recovery is reached for up to 10% ofdeformation. A tube made of this material could be more readily deformedover closer angles than a metallic tube. Moreover, a shape-memory effectexhibited by these alloys can be utilized to correct the roughly bentshape of the conduit before operation of the cooling system.

With reference to FIGS. 5 to 9, the heat sink 200 of the flexible heatcable device will be described. The heat sink 200 essentially consistsof a condenser unit 103, which has three main functions: (i) thecondenser unit 103 provides a surface that is kept at a lowertemperature than the saturation temperature of the vapour such that thevapour transferred through the heat transfer device 300 will contactthis surface and will condensate; (ii) the condenser section provides ameans by which the condensated liquid is able to flow backward into theboiling section of the heat collector device 100; and (iii) thecondenser section acts as a thermal interface to an external coolingsystem with a minimal thermal resistance.

The condenser unit 103, which is shown in FIG. 5, is connected to theconduit, i.e. the heat transfer device 300. The outer side of thecondenser unit 103 is attached to a cold-plate. Condensed liquid 104flows, under the effect of gravity, to the bottom part of the condenserplate and then back to the boiling chamber through the conduit walls.Evaporated liquid is introduced as vapour 105 into the condenser unit103.

Flow guides are provided to evenly distribute the liquid around theconduit entrance 302. A smooth surface or spirally configuredcorrugations of the conduit wall are to be preferred in order tominimize the liquid flow resistance. In order to cool down the condenserunit 103, a cold plate (not shown in the figures) is attached to athermal (cold plate) interface unit 201 of the condenser unit 103.

According to an exemplary embodiment of the present disclosure thethermal interface unit 201 is designed as a thermal plug for connectingthe condenser unit 103 of the heat sink 200 thermally and removably toan external cooling means. It is a major advantage of the presentdisclosure that an electronic device 101 can easily be connected anddisconnected to external units with both electrical and thermal links.

FIG. 6 exhibits details of the bottom part of the condenser unit 103.Shown in FIG. 6 are liquid channels 108 a-108 c where condensed liquidis accumulated and transferred back to the heat collector device 100(boiling section) via the walls of the heat transfer device 300.

In yet another exemplary embodiment of the present disclosure, asecondary liquid conduit is provided. The secondary liquid conduit isarranged inside the primary conduit and can be of a smaller size, sincethe volumetric flow rate of the liquid is much smaller than thevolumetric flow rate of the vapour. This secondary conduit is separatedfrom the outside of the primary conduit, wherein special sealingproperties have not to be provided. The main advantage of this design isthat it avoids re-entrainment limitations due to the friction betweenthe vapour and liquid in counter-flow.

FIG. 7 illustrates a modification of the condenser unit 103 shown inFIG. 5. Here, a separate hose, i.e. a liquid return hose 110, isprovided to return condensed liquid from the condenser unit 103 to theevaporator unit 102 of the heat collector device. Furthermore, acondensate collector 109 is provided to collect condensed vapour 105 andto guide it to the liquid return hose 110. Within the heat transferdevice 300, the liquid return hose 110 is connected to the heatcollector device 100 and the evaporator unit 102, respectively.

FIG. 8 exhibits details of the heat sink 200 depicted in FIG. 7.Especially, the construction of the condensate collector 109 is shown ingreater detail.

One disadvantage of the cold-plate design which is depicted in theprevious figures, is that the thermal contact resistance (i.e. thethermal interface) between the condenser plate and the cold-plate ishigh. This resistance, having high values, is able to hamper theperformance of the whole cooling apparatus. In order to overcome thisdrawback, FIGS. 10 and 11 exhibit another concept for cooling theevaporator unit 102 of the heat sink 200.

As shown in FIG. 10, cooling water 106 flows into the head of thecondenser unit 103 and exits the condenser unit at an opposite end. Thecooling water 106 is not used to cool a cold-plate, but it cools thecondenser unit 103 directly. Details of the flow path of the coolingwater 106 are depicted in FIG. 11. A direct contact between thecondenser unit 103 and the cooling water results in high heat transfercoefficients. The advantage of providing the condenser section and theoutside cold-channel as two separate parts is to minimize the dimensionsof the heat cable which aids the routing of the cable. Alternatively,several heat cable condensers can be plugged into a multi-cable-coredshell.

It is to be noted, that, although FIGS. 10 and 11 show a cylindricalconfiguration of the condenser unit 103, other units, i.e. rectangularforms or finned surfaces are also possible.

FIGS. 12 and 13 show yet another exemplary embodiment of the presentdisclosure. Wherein in the previous figures, the flow of the condensedliquid back to the evaporator unit 102 depends on gravity forces, thedevices shown in FIGS. 12 and 13 comprise a pump unit 112 in order topump back liquid, which has been collected in the condensate collector109. The liquid is pumped from the condensate collector 109 into theliquid return hose 110 by the pump unit 112.

If a liquid pump as a pump unit 112 is provided, the condenser unit 103can be placed below the evaporator unit 102 of the heat collector device100. One major advantage of a pumped two-phase system over asingle-phase—(i.e. only liquid circulation)—system is that a muchsmaller amount of liquid needs to be pumped for the same amount oftransferred energy. For example, in order to transfer 1000 W power with10° C. temperature difference at both ends approximately 1.5 l/min ofliquid water have to be pumped. The amount of liquid that must beevaporated and condensed for the same power level is only 26 ml/min (at1 atmosphere operation pressure). Consequently, the size and cost of thepump unit 112 in a two-phase system can be made smaller.

In order to provide a pump unit 112, diaphragm-type pumps are preferred.A diaphragm-type pump consists of a flexible membrane that is attachedto an oscillating mechanism driven by an electric motor. Two one-wayvalves provide intermittent but unidirectional flow. The flow circuit isinherently sealed from outside by the membrane and no shaft seals areneeded for the motor. In addition to that, diaphragm pumps can operatedry or with both liquid and gas mixtures.

According to yet another exemplary embodiment of the present disclosure,an alternative to an electrically powered pump is utilized, which usesenergy available in the external coolant liquid to pump the two-phaseloop.

A turbine-pump combination (i.e. a hydraulically actuated pump) isinserted between the external coolant and the internal condensatecircuits, as shown in FIG. 13. The mechanical energy provided by thecooling water 106 is extracted from the coolant at the pump unit 112,which is designed as a turbine, in order to pump the condensate. Thus asystem is created that can operate against gravity forces. In bothelectrical and hydraulic pumped loops, the pumps are located within thecondenser interface between a condenser collection chamber and theliquid return hose.

The exemplary embodiments of the present disclosure provide a coolingapparatus for electronic devices 101, to be cooled, wherein a flexibleheat transfer device 300 can be used to transfer heat from within anelectronic device 101 to be cooled to the outside without any openings.

It is an advantage that several electronic components can be groupedinto a high IP-class casing with air circulation inside. The circulationcan be facilitated either by a dedicated fan or by inherent cooling fansof the components. A flexible heat transfer device can then be used totransfer heat to the outside of the casing without interfering with thehigh IP-(Ingress Protection)-class of the whole electronic system.

The present disclosure provides a cooling apparatus, wherein a high heatand heat-density at the heat collector device is provided. An effectivecooling means at the condenser-site, such as direct water-cooling orinterfacing to a cold-plate, is provided.

It is a further aspect of embodiments of the present disclosure thatunknown geometry of an application site at the time of manufacturingposes no problem. The exact geometry of the cooling means of anapplication and the setting of the drive need not to be known. Theflexibility of the conduit with respect to general purpose interfacescan be provided.

The flexible heat cable device is an effective means to transfer heat tothe outside of a casing without diminishing theingress-protection-(IP)-class. This is especially important inindustrial environments.

While exemplary embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the disclosure. Accordingly, it is to beunderstood that the present disclosure has been described by way ofillustration and not limitation.

Furthermore, the disclosure is not limited to the specific applicationareas mentioned above.

It will be appreciated by those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. The presently disclosedembodiments are therefore considered in all respects to be illustrativeand not restricted. The scope of the invention is indicated by theappended claims rather than the foregoing description and all changesthat come within the meaning and range and equivalence thereof areintended to be embraced therein.

LIST OF REFERENCE NUMERALS

-   100 Heat collector device-   101 Electronic device-   102 Evaporator unit-   103 Condenser unit-   104 Liquid-   105 Vapor-   106 Cooling water-   107 Connector unit-   108 a- Liquid channel-   108 c-   109 Condensate collector-   110 Liquid return hose-   111 Sealing unit-   112 Pump unit-   200 Heat sink-   201 Thermal interface unit-   300 Heat transfer device-   301 Heat transfer direction-   302 Conduit entrance

1. A cooling apparatus for cooling an electronic device to be cooled,comprising: a) a heat collector device which is adapted to be in thermalcontact with the electronic device; b) a heat sink for absorbing heatwhich is emitted from the heat collector device and comprising acondenser unit and a thermal interface unit, wherein the condenser unitis cooled down via the thermal interface unit; c) a heat transfer devicemade from a flexible material for transferring heat which is emittedfrom the heat collector device to the heat sink, wherein d) the thermalinterface unit is designed as a thermal plug for connecting thecondenser unit of the heat sink thermally and removably to an externalcooling means.
 2. The cooling apparatus for cooling an electronic deviceas claimed in claim 1, wherein the heat transfer device includes anelectrical connection unit to simultaneously transfer thermal andelectrical energy between the electronic device and the heat sink. 3.The cooling apparatus for cooling an electronic device as claimed inclaim 1, wherein the electronic device forms an integral unit with theheat collector device.
 4. The cooling apparatus for cooling anelectronic device as claimed in claim 1, wherein the heat transferdevice is made of a thermoplastic polymer.
 5. The cooling apparatus forcooling an electronic device as claimed in claim 1, wherein the heattransfer device is made of at least one of polyethylene,polyethylene-terephthalate and polystyrene.
 6. The cooling apparatus forcooling an electronic device as claimed in claim 1, wherein the heattransfer device includes a metal layer deposited on the outer surface ofthe heat transfer device.
 7. The cooling apparatus for cooling anelectronic device as claimed in claim 1, wherein the heat transferdevice is made of super-elastic alloys.
 8. The cooling apparatus forcooling an electronic device as claimed in claim 1, wherein thecondenser unit comprises a pump unit for pumping back liquid, which hasbeen collected in a condensate collector.
 9. The cooling apparatus forcooling an electronic device as claimed in claim 8, wherein the pumpunit of the condenser unit is driven by the flow of cooling water. 10.The cooling apparatus for cooling an electronic device as claimed inclaim 1, wherein the heat collector device, the heat sink and the heattransfer device form a thermosyphon device.
 11. A method for cooling anelectronic device to be cooled, comprising the following steps: a)collecting heat from the electronic device to be cooled by a heatcollector device which is in thermal contact with the electronic deviceto be cooled; b) transferring heat which is emitted from the heatcollector device to a heat sink by means of a heat transfer device madefrom a flexible material c) absorbing heat which is emitted from theheat collector device by means of the heat sink comprising a condenserunit and a thermal interface unit, the thermal interface unit being athermal plug for connecting the condenser unit of the heat sinkthermally and removably to an external cooling means; and d) coolingdown the condenser unit via the thermal interface unit.
 12. The methodfor cooling an electronic device to be cooled as claimed in claim 11,wherein the heat sink is cooled by a secondary circulation of coolingwater.
 13. The method for cooling an electronic device to be cooled asclaimed in claim 11, wherein the heat transfer device transfers heatfrom the heat collector device to the heat sink by transporting a liquidcoolant from the heat collector device to the heat sink and by returningevaporated coolant from the heat sink to the heat collector device. 14.The method for cooling an electronic device to be cooled as claimed inclaim 12, wherein the condenser unit of the heat sink is directly cooledby the circulating cooling water.
 15. A cooling apparatus, comprising:a) a heat collector device adapted for a thermal contact; b) a heat sinkfor absorbing emitted heat, the heat sink including a condenser unit anda thermal interface unit; c) a heat transfer device formed of a flexiblematerial for transferring heat from the heat collector device to theheat sink; and d) an external cooling means, wherein the thermalinterface unit is configured as a thermal plug for connecting thecondenser unit of the heat sink thermally and removably to the externalcooling means.